Field of the Invention
The present invention relates to a process for continuous extraction of an aqueous and/or fat-containing liquid phase comprising aroma chemicals with a gas in the liquid or supercritical state.
Discussion of the Background
Aroma chemicals from various natural products are employed in various sectors such as foodstuffs and cosmetics but also pharmaceuticals. In the context of the present invention the term “aroma chemicals” is to be understood as meaning volatile compounds in foodstuffs which are perceived with the olfactory receptors either directly through the nose or via the pharynx during eating or drinking The literature describes in excess of 7000 relevant chemical compounds in this regard (RÖMPP Lexikon Lebensmittelchemie, ed. Gerhard Eisenbrand, Peter Schreier, 2nd edition, 2006, Georg-Thieme-Verlag, page 75).
Aroma chemicals from fruits for example are formed by from just a few dozen to several hundred chemical compounds depending on the plant species. These chemical compounds are in particular hydrocarbons (terpenes and sesquiterpenes) and oxygenated compounds (alcohols, aldehydes, ketones, acids, phenols, lactones, acetals, ethers and esters).
Aqueous solutions comprising fruit aromas are formed for example in the production of fruit juice concentrates: This involves concentration of fruit juices by evaporation. The fruit aromas present in the fruit vapours during the evaporation need to be added to the rediluted juice again before filling. However, the disadvantage of this aroma concentrate is its poor storage stability which is substantially attributable to the water content of the aroma extract. Processes to further concentrate the fruit aromas present in the fruit vapours have therefore been developed in the prior art, for example in EP 0 482 651 A1. These processes are based on using an extractant to extract the fruit aromas from the fruit vapours and thus further concentrate said aromas. It will be appreciated that there are also processes designed to remove undesired aroma chemicals from aqueous solutions. In this regard EP 0 041 723 A2 describes the extraction of aroma chemicals from brewer's yeast for example.
In addition to the extraction of aroma chemicals from aqueous solutions the extraction of aroma chemicals from more viscous media such as oils and fats is also of great economic interest and described in the prior art (WO 96/11043; R. Eggers & H. Wagner, J Supercrit Fluid 1993, 6, 31-37). As in the case of aqueous solutions in many cases it is the aroma chemicals in these oils and fats that are employed in cosmetics and/or foodstuffs.
This is the case especially for fats and oils of vegetable origin. For example, “Lexikon der pflanzlichen Fette and Öle”, 2nd edition, Springer-Verlag Vienna 2013, pages 218, 219, 262 describes the chemical compounds responsible for the aroma spectrum of the peanut and the hazelnut. These fats and oils of vegetable origin may be derived from the respective plant material by various processes such as vapour distillation and extraction for example (summarized in S. M. Pourmortazavi & S. S. Hajimirsadeghi, J Chromatogr A 2007, 1163, 2-24 for example).
However, in many cases unpleasant-smelling aroma chemicals must additionally be removed from oils and fats. This is in particular often the case when the oils and fats are of animal origin. In these cases it is not the unpleasant-smelling aroma chemicals but rather the oils and fats freed from the aroma chemicals which are of economic interest and are therefore subjected to further processing. Animal oils and fats may for example be generated during slaughtering or during meat or fish processing.
The prior art extraction processes employ gases in the liquid or supercritical state. The gas is very often supercritical CO2 which is employed under high pressure conditions (for example 264 bar, 50° C.). The extractant (supercritical CO2) is mixed with the phase for extraction in a column in countercurrent or in cocurrent which causes the aroma chemicals to be transferred from the phase for extraction into the extractant. The isolated aroma chemicals may then be separated from the laden supercritical CO2 in a further process step in which the latter is converted into the gaseous state by appropriate variation of the pressure and/or temperature and can therefore be removed easily. These processes are performed in continuous fashion.